HOW do you wire a house for ethernet ?
Isn't that a fat cable that ends in a larger USB type plug ?
How do you do it after the house is built ?
It's an RJ-45 jack that looks like an oversized telephone plug.
It's easy for your first floor if you have access through the basement ceiling to the floor, or have a crawl space. But from the nature of your questions, I see you would be hiring somebody for the work. I added a few outlets after the house was built. It's easier than adding an electrical outlet.
My router and switch are in the basement. I turned wifi off on the router. I installed my own wireless access points upstairs, connected to the ethernet.